This invention relates to improvements in small diameter, low profile dilatation catheters used in angioplasty, particularly coronary angioplasty. The invention concerns a type of angioplasty catheter commonly referred to as a "fixed wire" catheter in which the catheter includes a tubular shaft and an integral guidewire. More specifically, the invention concerns improvements in catheter systems and the manner in which such a catheter can be exchanged for another catheter.
In performing coronary angioplasty, the physician may wish to use a catheter different from the one originally inserted into the patient if the initial selection of catheter balloon size is inappropriate to treat the patient's stenosis or if some other event occurs that would make use of a different catheter desirable. When the catheter is the type that uses a separate movable guidewire, the catheter may be exchanged in a well-known procedure in which an exchange wire is substituted for the movable guidewire (or the length of the guidewire is extended with an extension wire). The catheter then is withdrawn over the exchange wire and the replacement catheter is threaded over the exchange wire and guided to the stenosis.
By maintaining the guidewire in position during the exchange procedure, the replacement catheter is easily and quickly advanced to the stenosis. Such procedure, however, has required the use of an "over-the-wire" catheter system which includes the catheter and a separate movable guidewire received through a guidewire lumen formed in the catheter. With an over-the-wire catheter system, the catheter is easily removed from the patient, leaving the guidewire extended in place so that the next succeeding catheter can be advanced over the guidewire to the site of the stenosis.
The foregoing catheter exchange procedure has not been usable with small diameter, low profile "fixed wire" dilatation catheters. These catheters incorporate an integral guidewire that cannot be separated from the catheter. Thus, when the physician desires to exchange one such dilatation catheter for another, the physician typically withdraws the entire catheter and integral guidewire from the patient's arterial system and then replaces it with the desired catheter.
Withdrawal of the catheter, however, results in loss of position of the catheter in the stenosis. As a result, the new catheter must be remanipulated through the patient's arterial system to position the balloon in the stenosis. This catheter replacement typically involves time-consuming manipulation and steering to guide the catheter and place its balloon within the stenosis. This additional procedure increases the risk of trauma and fluoroscopic radiation to the patient.
U.S. Pat. No. 4,932,959 to Horzewski et al. discloses a catheter having an inflatable collar for securing a portion of the wall forming the inner lumen to the guidewire when inflation fluid under pressure from a second annular passageway fills the inflation chamber. This construction demands a more complex construction and a three-arm adapter having independent sections communicating with individual catheter lumens.
It is therefore desirable to provide an improved system in which catheter exchanges involving small diameter, low profile dilatation catheters of the "fixed wire" type can be effected easily, quickly, with minimal trauma, and without loss of catheter position without complex design changes. It is among the objects of this invention to provide such a system.
It is therefore an object of the present invention to provide at improved angioplasty catheter arrangement having the advantages of a fixed wire catheter but which enables a catheter exchange to be performed without losing position of the guidewire in the patient.
Another object of the present invention is to provide a fixed wire type of angioplasty catheter having an elongate flexible shaft and an integral guidewire, in which the shaft is sealed to the guidewire at a joint that can be ruptured.
A further object of the invention is to provide an angioplasty catheter of the type described in which means are provided for enabling detachment of the shaft and balloon portion of the catheter from the guidewire.
A further object of the invention is to provide an improved method for performing angioplasty with a fixed wire type of catheter.
Additional objects and advantages of the invention will be set forth in the description which follows and, in part, will be obvious from the description and advantages being realized and attained by means of the instrumentation, facts, apparatus, systems, steps and procedures particularly pointed out in the specification.